Background: Residents of long-term care facilities have a high risk of acute care admission. Estimates of the frequency of inappropriate transfers vary substantially throughout the studies and various assessment tools have been used. The purpose of this study is to systematically review and describe the internationally existing assessment tools used for determining appropriateness of hospital admissions among long-term care residents. Method: Systematic review of the literature of two databases (PubMed and CINAHL®). The search covered seven languages and the period between January 2000 and December 2012. All quantitative studies were included if any assessment tool for appropriateness of hospital and/or emergency department admission of long-term care residents was used. Two pairs of independent researchers extracted the data. Results: Twenty-nine articles were included, covering study periods between 1991 and 2009. The proportion of admissions considered as inappropriate ranged from 2% to 77%. Throughout the studies, 16 different assessment tools were used; all were based on expert opinion to some extent; six also took into account published literature or interpretation of patient data. Variation between tools depended on the concepts studied, format and application, and aspects evaluated. Overall, the assessment tools covered six aspects: specific medical diagnoses (assessed by n = 8 tools), acuteness/severity of symptoms (n = 7), residents’ characteristics prior to admission (n = 6), residents’ or families’ wishes (n = 3), existence of a care plan (n = 1), and availability or requirement of resources (n = 10). Most tools judged appropriateness based on one fulfilled item; five tools judged appropriateness based on a balance of aspects. Five tools covered only one of these aspects and only six considered four or more aspects. Little information was available on the psychometric properties of the tools. Conclusions: Most assessment tools are not comprehensive and do not take into account residents’ individual aspects, such as characteristics of residents prior to admission and wishes of residents or families. The generalizability of the existing tools is unknown. Further research is needed to develop a tool that is evidence-based, comprehensive and generalizable to different regions or countries in order to assess the appropriateness of hospital admissions among long-term care residents.